JP3714365B1 - Keystone correction of projector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique for improving the correction accuracy in a projector that corrects image distortion caused by the tilt of the screen according to the observation result of the brightness distribution of the screen.
The present invention is a projector. This projector corrects distortion of an output image with respect to an input image caused by an inclination between a virtual projection plane assumed in advance and an actual projection plane. This correction is based on the image distortion caused by the inclination between the virtual projection plane and the actual projection plane according to the angle viewed from the image projection unit at the peak brightness position on the actual projection plane on which the correction image is projected. Estimate the amount. The correction image is configured such that the amount of change corresponding to the peak position movement amount of the angle when the peak position is viewed from the image projection unit is closer to the inclination angle than the all white pattern image.
[Selection] Figure 7

Description

  The present invention relates to a keystone correction technique for a projector.

  In recent years, projectors that project images on a screen have been rapidly spreading. In general, a projector is designed on the premise that the projector is arranged directly on the screen. Therefore, if the projector is not arranged on the screen, the image is distorted.

  On the other hand, when the projector is not arranged directly on the screen, not only the image but also the luminance distribution fluctuates. Furthermore, when the projector is equipped with an imaging device, the imaging distance differs between the left and right sides of the screen, so the amount of light received by the imaging device also varies between the left and right sides of the screen according to the inverse square theorem. Such fluctuations in the amount of received light can also be used to estimate the tilt of the screen with respect to the optical axis of the projector.

JP 2000-241874 A

  However, there is a problem that the variation in the amount of received light varies not only due to the tilt of the screen, but also due to the illuminance distribution when the projector is arranged facing the screen.

  The present invention has been made to solve the above-described problems in the prior art, and is a technique for improving correction accuracy in a projector that corrects image distortion caused by screen tilt according to the distribution of screen brightness. The purpose is to provide.

The present invention is a projector. This projector
An image projection unit configured to project an image according to an input image on a virtual projection plane arranged in a predetermined positional relationship set in advance;
An output image capturing unit that captures an output image projected on an actual projection plane;
An imaging information generation unit that outputs imaging information including brightness information having a correlation with brightness according to the captured image;
A distortion correction unit that corrects the distortion of the output image with respect to the input image caused by the inclination between the virtual projection plane and the actual projection plane according to the imaging information;
With
The distortion correction unit
A correction image supply unit that supplies a correction image for use in compensating for distortion of the output image to the image projection unit;
In accordance with the imaging information, a peak position movement amount, which is a movement amount of a peak position from a brightness peak position on the virtual projection plane to a brightness peak position on the actual projection plane, is determined and determined. An image processing unit that distorts the input image in advance so that the distortion of the output image is compensated according to the peak position movement amount,
Have
The correction image is configured such that the amount of change of the angle of the peak position viewed from the image projection unit according to the amount of movement of the peak position is closer to the angle of inclination than the all white pattern image. It is characterized by that.

In the projector according to the present invention, the correction image configured such that the amount of change according to the peak position movement amount of the angle viewed from the image projection unit of the peak position is closer to the inclination angle than the all white pattern image. Since the inclination of the projection plane is estimated using this, the factor of the measurement error of the inclination is reduced. As a result, it is possible to realize compensation for image distortion due to the inclination of the screen with high accuracy.

In the above projector,
The image processing unit
In accordance with the imaging information, a peak position angle determination unit that determines a peak position angle as viewed from the image projection unit of a brightness peak position on the actual projection plane;
According to a peak position angle movement amount that is a movement amount of an angle from a reference peak position angle that is an angle viewed from the image projection unit of a brightness peak position on the virtual projection plane to the determined peak position angle An inclination angle estimating unit for estimating an angle of the inclination,
An image deformation unit that distorts the input image in advance so that distortion of the output image is compensated according to the estimated angle of inclination;
You may make it have.

  In the projector, the correction image may be configured such that the illuminance distribution on the virtual projection plane is more uniform than the all white pattern image.

  In this way, the correction image can be easily configured so that the amount of movement of the brightness peak position is close to the angle shift between the virtual projection plane and the actual projection plane.

  In the projector, the correction image may be configured such that an illuminance ratio on the virtual projection plane is between 85% and 95%.

  In the projector, the distortion correction unit may correct the image for correction according to the imaging information so as to be close to the deviation of the angle in a state where the actual projection plane is aligned with the virtual projection plane. You may make it have the calibration mode which is an operation mode for reconfiguring.

  By so doing, it is possible to suppress a decrease in measurement accuracy due to aging of optical system components such as an illumination optical system and a liquid crystal panel.

  The present invention is embodied in a carrier including a projector, a projector control apparatus, a computer program and firmware for causing a computer to implement the functions of the method or apparatus, a recording medium storing the computer program, and the computer program. It can be realized in various forms such as a consumable container provided with a recorded data signal and a storage device.

Next, embodiments of the present invention will be described in the following order based on examples.
A. Basic configuration of LCD projector:
B. Estimation of relative angle when the illumination ratio of the optical system is 100%:
C. Estimation of relative angle when the illumination ratio of the optical system is 80%:
D. Trapezoidal distortion correction processing in the embodiment of the present invention:
E. Variation:

A. Basic projector configuration:
FIG. 1 is a block diagram showing a configuration of a liquid crystal projector 10 as an embodiment of the present invention. The liquid crystal projector 10 includes an optical system 100 for projecting an image on a screen SC and a control system 200 for controlling projection light. The optical system 100 includes an illumination optical system 110, a liquid crystal panel (LCD) 120, and a projection optical system 130. The control system 200 includes a controller 210, an image processing unit 220, a liquid crystal panel (LCD) driver 230, a captured image analysis unit 260, and an imaging unit 250.

  The controller 210 includes a CPU and a memory (not shown). The controller 210 controls the image processing unit 220, the LCD driver 230, and the captured image analysis unit 260.

  The image processing unit 220 processes an input image signal given from the outside and generates an input signal to the LCD driver 230. The processing of the input image signal includes various image processing such as image quality adjustment processing and trapezoid correction processing. The image quality adjustment processing includes processing such as brightness adjustment and color temperature correction. The trapezoidal correction process is a process for correcting image distortion (trapezoidal distortion) that occurs when the screen SC does not face the optical axis of the optical system 100 of the liquid crystal projector 10.

  The LCD driver 230 generates a drive signal for driving the liquid crystal panel 120 based on the image data input from the image processing unit 220. This drive signal is supplied to the liquid crystal panel 120 and used to control the amount of transmitted light of each pixel included in the liquid crystal panel 120. The light transmitted through the liquid crystal panel 120 is irradiated to the projection optical system 130.

  The projection optical system 130 projects the light emitted from the liquid crystal panel 120 onto the screen SC. The screen SC is irradiated with a predetermined illuminance ratio by the projection light. Here, the irradiation state on the screen SC is imaged by the imaging unit 250.

  FIG. 2 is an explanatory diagram showing an equipped state of the imaging unit 250 in the embodiment of the present invention. The imaging unit 250 is equipped in the vicinity of the projection optical system 130 of the liquid crystal projector 10 so as to have an optical axis parallel to the projection optical system 130. The imaging unit 250 has a viewing angle that covers the irradiation range of the projection optical system 130.

  In the present embodiment, the imaging unit 250 uses a hatched area as an observation area for easy understanding of the description. This observation area is an area set at almost the same height as the projection optical system 130. In this embodiment, brightness is observed discretely in this region.

B. Estimation of relative angle when the illumination ratio of the optical system is 100%:
FIG. 3 is an explanatory view showing a projection state in the embodiment of the present invention. FIG. 3A is a view of the relative position of the liquid crystal projector 10 and the screen SC as viewed from above. The liquid crystal projector 10 has an irradiation range of 60 degrees on the left and right. In this embodiment, each position on the projection surface of the screen SC is defined by each coordinate centered on the optical principal point of the projection optical system 130. In FIG. 3, the projection surface of the screen SC is assumed to be arranged on the “virtual projection surface” in the claims.

  FIG. 3B shows the illuminance at each position on the projection surface of the screen SC. In this example, since the projection optical system 130 is configured to have an illuminance ratio of 100% when a 100% all white pattern image is projected, the projection surface of the screen SC is uniform in the irradiation range of the projection optical system 130. Has an illuminance of. Here, the “illuminance ratio” means the illuminance ratio between the central point and the peripheral part of the projection image, and the illuminance ratio of 100% means that the illuminances at the central point and the peripheral part match.

  FIG. 3C shows the amount of light received by a sensor surface (not shown) due to light received from the projection surface of the screen SC. On the sensor surface, the surface of the screen SC is projected by an optical system (not shown) of the imaging unit 250. As can be seen from FIG. 3C, the amount of light received on the sensor surface is not uniform even though the illuminance on the projection surface of the screen SC is uniform. This is because each part of the projection surface of the screen SC can be regarded as a point light source, and the irradiated light reaches the sensor surface according to Lambert's cosine law and inverse square law. Here, in order to make the explanation easy to understand, the projection surface of the screen SC is assumed to be a complete diffusion surface.

  The Lambert's cosine law is a law that the light beam received from the light emitting surface at the observation point is proportional to the cosine of the angle θ between the normal line of the light emitting surface and the line connecting the observation point and the light emitting surface. On the other hand, the inverse square law is a law that the light flux received by the observation point from the light emitting surface is inversely proportional to the square of the distance between the observation point and the light emission surface.

As a result, the received light amount of the sensor surface from each part of the projection surface of the screen SC (FIG. 3C) is COS ³ θ ÷ R0 ² (= COSθ ÷ () with respect to the illuminance of each part of the projection surface of the screen SC. R0 ÷ COSθ) ² ).

  FIG. 4 is an explanatory diagram showing a projection state when the screen SC is inclined at an angle α with respect to the optical axis of the projection optical system 130. FIG. 4A is a diagram of the relative positions of the liquid crystal projector 10 and the screen SC having an inclination of α degrees as viewed from above. FIG. 4B shows the illuminance at each position on the projection surface of the screen SC having an inclination of α degrees.

  As can be seen from FIG. 4B, the illuminance at each position on the projection surface of the screen SC increases toward the left side. For example, the illuminance at the point P1 on the screen SC has an illuminance of a magnitude obtained by multiplying the illuminance at the point P1 ′ by the square of the projection distance ratio (R1 ′ / R1). The illuminance has a magnitude obtained by multiplying the illuminance at the point P2 ′ by the square of the ratio (R2 ′ / R2) of the projection distance. On the other hand, the ratio of the projection distance increases as it goes to the left.

  FIG. 5 shows the amount of light received by the sensor surface when the screen SC is tilted at an angle α with respect to the optical axis of the projection optical system 130 and when the screen SC is not tilted. FIG. 5A is the same diagram as FIG. FIG. 5B is a value derived from the values in FIG. 5A according to Lambert's cosine law and inverse square law.

  As can be seen from FIG. 5B, the peak of the received light amount distribution on the sensor surface is shifted to the left according to the inclination of the screen SC. In the example of this figure, the shift amount is δ1 degrees. Since the shift amount varies according to the tilt of the screen SC, it can be seen that the tilt of the screen SC can be estimated based on the shift amount.

  In this way, it can be theoretically understood that the relative positional relationship (angle) between the projector and the screen can be estimated in accordance with the shift amount of the illuminance peak on the screen SC. However, it should be noted that the shift amount and the inclination of the screen SC do not necessarily match.

C. Estimation of relative angle when the illumination ratio of the optical system is 80%:
FIG. 6 is an explanatory diagram showing the illuminance distribution of the screen SC and the received light amount distribution on the sensor surface when the illuminance ratio of the optical system is 80%. FIG. 6A shows the illuminance distribution of the screen SC. In this example, the illuminance at both the left and right ends is 80% of the illuminance at the center.

  FIG. 6B shows the received light amount distribution on the sensor surface when the screen SC is not inclined. The two-dot chain line indicates the received light amount distribution when the illuminance ratio Lr is 100%, which is equal to the received light amount distribution in FIG. The solid line indicates the received light amount distribution when the illuminance ratio Lr is 80%. As can be seen from FIG. 6B, when the illuminance ratio Lr is 80%, the received light amount at the central portion is higher and the received light amount at the peripheral portion is lower than when the illuminance ratio Lr is 100%. Tend.

  FIG. 6C shows the received light amount distribution on the sensor surface with and without the screen SC being inclined. Similar to the diagram of FIG. 5B, the peak of the received light amount distribution on the sensor surface is shifted to the left according to the inclination of the screen SC. However, the shift amount is reduced from δ1 degrees to δ2 degrees. This means that the shift amount varies not only according to the inclination of the screen SC but also according to the illuminance ratio of the projection optical system 130.

  Here, as a general tendency of the optical system of the projector, there is a trade-off relationship between the illuminance and the illuminance ratio. That is, when the illuminance ratio is increased, the illuminance tends to decrease. For this reason, a general projector is designed to increase the illuminance while suppressing the illuminance ratio, so the illuminance ratio is about 80%.

  In this embodiment, when the illuminance ratio Lr is 100%, the shift amount (angle) is larger than the inclination angle of the screen SC, whereas when the illuminance ratio Lr is 80%, the shift amount (angle). Is smaller than the angle of inclination of the screen SC. This means that if the illuminance ratio Lr is set appropriately, the shift amount can be configured to match the inclination angle of the screen SC.

  Further, it has been found through experiments that a general projector optical system can be configured so that the shift amount substantially matches the inclination angle of the screen SC when the illuminance ratio is in the range of 85% to 95%.

D. Trapezoidal distortion correction processing in the embodiment of the present invention:
FIG. 7 is a flowchart showing a trapezoidal distortion correction processing routine in the embodiment of the present invention. In this embodiment, it is assumed that there is no inclination in the vertical direction for easy understanding of the description. For this reason, in the trapezoidal distortion correction process in the embodiment of the present invention, only the horizontal screen inclination is measured.

  In step S100, the liquid crystal projector 10 projects the correction image on the screen SC. The correction image is an image configured such that the illuminance ratio of the projection surface of the screen SC is 90%. The correction image is configured to reduce the amount of light projected onto the central portion of the screen SC by adjusting the amount of light transmitted through the liquid crystal panel 120 with respect to the all white pattern image, thereby realizing an illuminance ratio of 90%. Yes.

  In step S200, the imaging unit 250 (FIGS. 1 and 2) performs an imaging process. The imaging process is a process of measuring the amount of light from a predetermined imaging area in the area where the correction image is projected. In this embodiment, the predetermined imaging area is the hatching area shown in FIG. The measured light quantity corresponds to “brightness information” in the claims.

  In step S300, the liquid crystal projector 10 projects an all black pattern image on the screen SC. The all black pattern image is an image configured to minimize the amount of light transmitted through the liquid crystal panel 120.

  In step S400, the imaging unit 250 performs an imaging process. The reason for capturing the all black pattern image is to obtain the difference from the correction image and suppress the influence of the ambient light.

  In step S500, the captured image analysis unit 260 performs sensor received light amount analysis processing. The sensor light reception amount analysis processing is a difference between the light reception amounts acquired by projecting the correction image and the all black pattern image for each instantaneous visual field of the sensor (not shown) and is the optical center of the projection optical system 130. This is a process of mapping to an angular coordinate system based on the principal point.

  In step S600, the captured image analysis unit 260 estimates the inclination of the screen SC. The inclination of the screen SC is determined according to the angle of the peak position of the received light amount with respect to the optical axis of the projection optical system 130.

  The peak position may be determined by simple comparison of the received light amount mapped to the angular coordinate system as shown in FIG. 8A, for example (δ2 ′), for example, FIG. 8B. As shown in FIG. 5, it may be determined (δ2 ″) by a curve approximation method (curve fitting) using the least square method. The former has the advantage that the algorithm is simple and the calculation process is simple, and the latter has the advantage that the estimation error of the angle of the screen SC due to the measurement noise of the received light amount becomes small. The curve approximation method also has an effect that the influence of noise can be reduced even when a large noise is placed near the peak position.

  The inclination of the screen SC estimated in this way is sent from the captured image analysis unit 260 (FIG. 1) to the image processing unit 220.

  In step S700, the image processing unit 220 determines a keystone correction amount. The keystone correction is a process of distorting an image projected in advance in the reverse direction so that image distortion caused by the inclination of the screen SC is reduced (that is, compensated). The trapezoidal correction amount means the amount of distortion in the reverse direction.

  FIG. 9 is an explanatory diagram showing the relationship between the inclination of the screen SC and the trapezoidal correction amount in the embodiment of the present invention. As can be seen from FIG. 9, the correction amount increases as the inclination of the screen SC increases. The correction amount increases as the inclination of the screen SC increases because the distance from the principal point of the projection optical system 130 to the projection surface of the screen SC varies greatly from left to right as the inclination of the screen SC increases. is there.

  In step S800, the liquid crystal projector 10 projects the trapezoidally corrected image. The projection of the trapezoidally corrected image is performed by the image processing unit 220 projecting the projected image after distorting it in advance with the determined trapezoidal correction amount.

  As described above, in this embodiment, the angle shift is performed using the correction image configured such that the movement amount of the brightness peak position matches the angle shift between the virtual projection plane and the actual projection plane. Since it is measured, the angle deviation can be directly measured based on the movement amount of the peak position.

E. Variation:
The present invention is not limited to the above-described examples and embodiments, and can be implemented in various modes without departing from the gist thereof. For example, the following modifications are possible.

E-1. In the embodiment described above, only the horizontal screen SC inclination is estimated and only the horizontal keystone correction is executed. However, the vertical keystone correction may be combined. The estimation of the angle in the vertical direction may be performed by the liquid crystal projector 10 using, for example, a sensor built in a tilt mechanism that adjusts the optical axis in the direction of gravity or the vertical direction, or a brightness peak. You may make it measure according to the moving amount | distance of the up-down direction of a position. Further, the vertical keystone correction may be performed independently according to the above-described embodiment.

  It should be noted that the “angle deviation between the virtual projection plane and the actual projection plane” in the claims means an angle deviation that occurs in at least one of the horizontal direction and the vertical direction.

E-2. In the above-described embodiment, the correction image is configured such that the peak position movement amount matches the angle shift, but it is not always necessary to make it completely match. For example, an angle difference between the peak position shift amount and the angle shift is stored in a memory (not shown) of the liquid crystal projector 10 at the time of manufacture, and the angle shift is determined using the angle difference and the peak position shift amount. You may make it do. In the present invention, in general, it is only necessary that the correction image is configured so that the peak position movement amount is closer to the angle shift than the all white pattern image. However, the above-described embodiment has an advantage that the measurement error due to the above-described angle difference can be reduced.

E-3. In the above-described embodiment, the correction image is configured so that the peak position movement amount is close to the angle shift by adjusting the illuminance ratio and the uniformity of the illuminance distribution, and adjusting the illuminance ratio and the illuminance distribution. It is sufficient that the amount is configured to be close to the angle deviation, and the pattern of the correction image may be configured regardless of the illuminance ratio and the uniformity of the illuminance distribution.

E-4. In the above-described embodiment, the image projection unit is configured such that the optical axis thereof is arranged so as to face the screen SC in a direction perpendicular to the horizontal direction. For example, the image projection unit is arranged obliquely in the horizontal direction. You may comprise as a premise. The image projection unit used in the present invention only needs to be configured to project an image on a virtual projection plane arranged in a predetermined positional relationship set in advance, and the virtual projection plane is on the optical axis of the image projection unit. There is no need to face it vertically.

E-5. In the above-described embodiment, the influence of ambient light is suppressed by projecting and imaging an all black pattern, but the projection of the all black pattern is not essential and can be omitted. The projection of the all black pattern has an advantage that the measurement accuracy can be improved by suppressing the influence of ambient light.

E-6. The liquid crystal projector and other projectors further have a calibration mode that is an operation mode for reconstructing a correction image in accordance with imaging information in a state where the actual projection plane is arranged to coincide with the virtual projection plane. It is preferable to do.

  This calibration mode is realized by providing means (for example, a switch or an interface screen) for making an input to inform the projector that the actual projection plane is arranged so as to coincide with the virtual projection plane. Can do. This is because it is possible to suppress a decrease in measurement accuracy due to aging of optical system components such as an illumination optical system and a liquid crystal panel (or DMD (registered trademark) panel).

E-7. In the above-described embodiment, the present invention is configured as the liquid crystal projector 10, but may be configured as a projector of another system such as a DLP (registered trademark) system or a three-tube system. Furthermore, in the above-described embodiments, the present invention is configured as a front projector, but can be applied to, for example, a rear projector.

E-8. In the above-described embodiment, the angle is used as a variable representing the shift amount of the peak position in the above-described embodiment. However, for example, the trapezoid correction amount is determined using the pixel position of a sensor (not shown) included in the imaging device. It may be configured. In general, the image processing unit of the present invention may be configured to distort an input image in advance so that distortion of the output image is compensated according to the peak position movement amount.

E-9. In the above-described embodiment, the correction image is configured to be realized by adjusting the transmitted light amount of the liquid crystal panel 120 with respect to the all white pattern image to reduce the transmitted light amount to the central portion of the screen SC. The correction image may be configured with reference to a pattern other than the all white pattern image. That is, it is not always necessary to maximize the amount of transmitted light of the pixel with the highest brightness of the correction image, and only the illuminance ratio on the screen becomes a problem.

  When some or all of the functions of the present invention are realized by software, the software (computer program) can be provided in a form stored in a computer-readable recording medium. In the present invention, the “computer-readable recording medium” is not limited to a portable recording medium such as a flexible disk or a CD-ROM, but an internal storage device in a computer such as various RAMs and ROMs, a hard disk, and the like. An external storage device fixed to the computer is also included.

1 is a block diagram showing a configuration of a liquid crystal projector 10 as an embodiment of the present invention. Explanatory drawing which shows the equipment state of the imaging part 250 in the Example of this invention. Explanatory drawing which shows the projection state in the Example of this invention. 4 is an explanatory diagram showing a projection state when the screen SC is inclined at an angle α with respect to the optical axis of the projection optical system 130. FIG. The amount of light received by the sensor surface when the screen SC is tilted at an angle α with respect to the optical axis of the projection optical system 130 and when the screen SC is not tilted. Explanatory drawing which shows the illumination intensity distribution of the screen SC in case the illumination ratio of an optical system is 80%, and the received light amount distribution of a sensor surface. The flowchart which shows the routine of the trapezoid distortion correction process in the Example of this invention. Explanatory drawing which shows the mode of the determination of the peak position in the Example of this invention. Explanatory drawing which shows the relationship between the inclination of screen SC and the trapezoid correction amount in the Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Liquid crystal projector 100 ... Optical system 100 ... Illuminance ratio 110 ... Illumination optical system 120 ... Liquid crystal panel 130 ... Projection optical system 200 ... Control system 210 ... Controller 220 ... Image processing part 230 ... LCD driver 230 ... Driver 230 ... Liquid crystal panel driver 250: Imaging unit 260 ... Captured image analysis unit

Claims (6)

A projector,
An image projection unit configured to project an image according to an input image on a virtual projection plane arranged in a predetermined positional relationship set in advance;
An output image capturing unit that captures an output image projected on an actual projection plane;
An imaging information generation unit that outputs imaging information including brightness information having a correlation with brightness according to the captured image;
A distortion correction unit that corrects the distortion of the output image with respect to the input image caused by the inclination between the virtual projection plane and the actual projection plane according to the imaging information;
With
The distortion correction unit
A correction image supply unit that supplies a correction image for use in compensating for distortion of the output image to the image projection unit;
In accordance with the imaging information, a peak position movement amount, which is a movement amount of a peak position from a brightness peak position on the virtual projection plane to a brightness peak position on the actual projection plane, is determined and determined. An image processing unit that distorts the input image in advance so that the distortion of the output image is compensated according to the peak position movement amount,
Have
The correction image is configured such that the amount of change of the angle of the peak position viewed from the image projection unit according to the amount of movement of the peak position is closer to the angle of inclination than the all white pattern image. A projector characterized by that. The projector according to claim 1, wherein
The image processing unit
In accordance with the imaging information, a peak position angle determination unit that determines a peak position angle as viewed from the image projection unit of a brightness peak position on the actual projection plane;
According to a peak position angle movement amount that is a movement amount of an angle from a reference peak position angle that is an angle viewed from the image projection unit of a brightness peak position on the virtual projection plane to the determined peak position angle An inclination angle estimating unit for estimating an angle of the inclination,
An image deformation unit that distorts the input image in advance so that distortion of the output image is compensated according to the estimated angle of inclination;
Having a projector. The projector according to claim 1 or 2,
The correction image is configured such that the illuminance distribution on the virtual projection plane is more uniform than the all-white pattern image. The projector according to any one of claims 1 to 3,
The projector, wherein the correction image is configured such that an illuminance ratio on the virtual projection plane is between 85% and 95%. The projector according to any one of claims 1 to 4,
The distortion correction unit has a calibration mode which is an operation mode for reconstructing the correction image according to the imaging information in a state where the actual projection plane is arranged to coincide with the virtual projection plane. A projector. A method of projecting an image using an image projection unit configured to project an image according to an input image on a virtual projection plane arranged in a predetermined positional relationship set in advance,
(A) capturing an output image projected on an actual projection surface;
(B) outputting imaging information including brightness information having a correlation with brightness according to the captured image;
(C) correcting distortion of the output image with respect to the input image caused by an inclination between the virtual projection plane and the actual projection plane according to the imaging information;
With
The step (c)
Supplying a correction image for use in compensating for distortion of the output image to the image projection unit;
In accordance with the imaging information, a peak position movement amount, which is a movement amount of a peak position from a brightness peak position on the virtual projection plane to a brightness peak position on the actual projection plane, is determined and determined. Predistorting the input image so that distortion of the output image is compensated according to the peak position movement amount,
Including
The correction image is configured such that the amount of change of the angle of the peak position viewed from the image projection unit according to the amount of movement of the peak position is closer to the angle of inclination than the all white pattern image. An image projection method characterized by the above.

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